1. Field of the Invention
The present invention relates to a multidirectional input device that permits the simultaneous operation of a plurality of electric parts through the operation of a single operating shaft.
2. Description of the Related Art
As shown in FIG. 20, a conventional multidirectional input device has a box-shaped case 31. At the center of a top plate 31a of this case 31, there is formed a hole 31b. First and second interlock members 32 and 33 are rotatably supported in the case 31 so as to cross each other at right angles.
The first interlock member 32 has a substantially U-shaped connecting portion 32a. A first elongated hole 32b extends longitudinally through the connecting portion 32a. The lower portion of one end portion of the connecting portion 32a comprises an engagement claw 32c protruding in a direction parallel to the longitudinal direction of the connecting portion 32a. The lower portion of each end portion of the connecting portion 32a further comprise protrusions 32d protruding in a direction perpendicular to the engagement claw 32c. 
Below the first interlock member 32, there is disposed a second interlock member 33 configured so as to extend in a direction perpendicular to the first interlock member 32. This second interlock member 33 has a bar-like connecting portion 33a and a second elongated hole 33b extending longitudinally through the connecting portion 33a. 
At one end portion of the connecting portion 33a, there protrudes an engagement claw 33c in a direction parallel to the longitudinal direction of the connecting portion 33a. Each end portion of the connecting portion 33a further comprises protrusions 33d protruding in a direction perpendicular to the engagement claw 33c. A shaft support hole 33e extends through the second elongated hole 33b. 
An operating shaft 34 is disposed through the hole 31a of the case 31. This operating shaft 34 has a bar-like cylindrical portion 34a. Below this cylindrical portion 34a, there is formed a flat portion 34b. A protrusion 34c protrudes downwardly from this flat portion 34b. Further, a support hole 34d extends through the flat portion 34b. 
The operating shaft 34 is connected to the second interlock member 33 by pin 39, which extends through the shaft support holes 33e in the second interlock member 33 and the shaft support hole 34d in the flat portion 34b of the operating shaft 34. The cylinder portion 34a extends upwardly through the first elongated hole 32b of the first interlock member 32.
A rotary electric part, such as a variable resistor 35, is mounted to a first side plate 31c of the case 31 (shown on the left-hand side of FIG. 20). A second variable resistor 35 (not shown in FIG. 20) is connected to the second side plate 31d, which is perpendicular to the first side plate 31c. The variable resistor 35 consists of a substrate 35a and a slider receiver 35b. In this slider receiver 35b, there is provided an engagement hole 35c which can be engaged with the engagement claws 32c and 33c of the first and second interlock members 32 and 33.
Below the first and second interlock members 32 and 33, there is disposed a substantially square push-up member 36. The push-up member 36 includes an abutment portion 36a against which the protrusion 32d of the first interlock member 32 can abut, and an abutment portion 36b against which the protrusion 33d of the second interlock member 33 can abut, each being formed near the corner portion of the push-up member 36. A hole 36c is provided through the central portion of the push-up member 36.
A coil spring 37 is positioned below the push-up member 36, and is mounted to a bottom plate 38 so as to provide an elastic biasing force against the push-up member 36. Thus, the push-up member 36 is pushed up towards the first and second interlock members 32 and 33 by the coil spring 37.
When the operating shaft 34 of this conventional multidirectional input device is inclined in the direction of the arrow A (as shown in FIG. 21A), the flat portion 34b rotates within the second elongated hole 33b by using the pin 39 as a fulcrum. At the same time, the first interlock member 32 rotates using the protrusions 32d at both ends as fulcrums, thereby making it possible to operate the variable resistor 35 engaged with the engagement claw 32c. 
As shown in FIG. 21B, when the operating shaft 34 is inclined in the direction of the arrow B, the cylindrical portion 34a of the operating shaft 34 moves along the first elongated hole 32b of the first interlock member 32. At the same time, the second interlock member 33 rotates using the protrusions 33d as fulcrums, thereby making it possible to operate the variable resistor 35 engaged with the engagement claw 33c. 
When the force that has been applied in the direction of the arrow A or B of the operating shaft 34 is cancelled, the push-up member 36 is pushed upward by the elastic force of the coil spring 37, causing the first and second interlock members 32 and 33 to rotate to their initial attitude. The operating shaft 34 is therefore automatically restored to the vertical neutral position.
In this conventional multidirectional input device, it is possible to simultaneously operate two variable resistors mounted to the case 31 by inclining the operating shaft 34 in both the A and B directions. For example, it is possible to easily perform input operation through a cursor or the like on the display of a personal computer.
However, in the conventional multidirectional input device described above, the connecting portion 32a of the first interlock member 32 is disposed above the second interlock member 33 so as to be astride the second interlock member 33. In addition, a large gap must be formed between the top plate 31a of the case 31 and the second interlock member 33 so that the connecting portion 32a can freely rotate. As a result, it is difficult to achieve a reduction in the thickness of the conventional multidirectional input device.
Further, the positions at which the protrusions 32d and 33d of the first and second interlock members 32 and 33, respectively, abut the push-up member 36 are offset from the center of the operating shaft 34. Consequently, when the push-up member 36 is pushed downwardly by the rotation of the first or second interlock member 32 or 33, the push-up member 36 can be tilted. This results in the generation of friction and a creaking noise in the central hole 36c and the guide portion 38a of the bottom plate 38.
It is therefore impossible to smoothly push down the push-up member 36, with the resultant deterioration of the operational feeling of the operating shaft 34.
Further, the position of the lower end portion of the coil spring 37 tends to slide when the push-down member 36 is vertically moved, causing a variation in the biasing force of the coil spring 37 on the push-down member 36. This results in an unstable operational force needed to incline the operating shaft 34.
Accordingly, it is an object of the present invention to overcome the above problems. In particular, it is an object of the present invention to provide a high-performance multidirectional input device having a reduction in thickness, a superior operational feeling for the operating shaft, and a constant operating force needed for inclining the operating shaft.
As a first embodiment for solving the above problems, there is provided a multidirectional input device comprising a first interlock member that is rotatable and has a first elongated hole, a second interlock member that is arranged in a direction perpendicular to the first interlock member, that is rotatable and which has a second elongated hole, and a frame body supporting the first and second interlock members inside. An operating shaft is inserted through the first elongated hole and is rotatably supported by the first interlock member so as to be capable of inclining along the first elongated hole. A coil spring provides an elastic biasing force from below the first and second interlock members. A plurality of electric parts are connected to and operated by the first and second interlock members. Support portions are provided at both ends of the first and second interlock members for supporting the first and second interlock members inside the frame body. Wherein the second interlock member has between the support portions a connecting portion having a second elongated hole, and the connecting portion is arranged below the first interlock member so as to be astride the first interlock member, the connecting portion being positioned in the inner peripheral portion of the coil spring.
Further, as a second embodiment for solving the above problems, there is provided a multidirectional input device, wherein the connecting portion is formed in an arcuate configuration, the center of which is positioned at a rotatably supporting portion that rotatably supports the operating shaft of the first interlock member.
Further, as a third embodiment for solving the above problems, there is provided a multidirectional input device, wherein the support portions of the first and second interlock members are positioned at the same height as the frame body.
Further, as a fourth embodiment for solving the above problems, there is provided a multidirectional input device, wherein the coil spring elastically biases the portions in the vicinity of the support portions of the first and second interlock members.
Further, as a fifth embodiment for solving the above problems, there is provided a multidirectional input device, wherein there is provided between the first and second interlock members and the coil spring a spring receiving member capable of performing the positioning of the coil spring, and wherein the movement of the spring receiving member when the first and second interlock members are rotated is guided by the first and second interlock members.
Further, as a sixth embodiment for solving the above problems, there is provided a multidirectional input device, wherein there is provided below the first and second interlock members a guide portion capable of guiding the movement of the spring receiving member.
Further, as a seventh embodiment for solving the above problems, there is provided a multidirectional input device, wherein the guide portion is formed in the vicinity of the support portions of the first and second interlock members, and wherein either the outer peripheral portion or the inner peripheral portion of the spring receiving member can be guided by the guide portion.
Further, as an eighth embodiment for solving the above problems, there is provided a multidirectional input device, wherein the inner peripheral portion of the spring receiving member is positioned at the connecting portion of the second interlock member so as to guide the movement of the spring receiving member.
Further, as a ninth embodiment for solving the above problems, there is provided a multidirectional input device, wherein the guide surface constituting the guide portion is formed in a tapered configuration.
Further, as a tenth embodiment for solving the above problems, there is provided a multidirectional input device, wherein the spring receiving member is provided with a positioning portion for performing the positioning of the upper end portion of the coil spring.
Further, as an eleventh embodiment for solving the above problems, there is provided a multidirectional input device, wherein the positioning portion is formed so as to be capable of performing the positioning of at least either the outer peripheral portion or the inner peripheral portion of the coil spring.
Further, as a twelfth embodiment for solving the above problems, there is provided a multidirectional input device, wherein there is formed in the positioning portion of the spring receiving portion an escape portion for escaping from a step generated at the start of the winding of the coil spring.
Further, as a thirteenth embodiment for solving the above problems, there is provided a multidirectional input device, wherein the frame body has a bottom plate for closing the lower portion, and wherein there is formed in this bottom plate a positioning groove for performing the positioning of the lower end portion of the coil spring.
Further, as a fourteenth embodiment for solving the above problems, there is provided a multidirectional input device, wherein there is formed in the positioning groove of the bottom plate an escape portion for escaping from a step generated at the end of the winding of the coil spring.
Further, as a fifteenth embodiment for solving the above problems, there is provided a multidirectional input device, wherein there is formed in the bottom plate a restricting portion for restricting the downward movement of the operating shaft when a pressurizing load is applied to the operating shaft, and wherein when the operating shaft is downwardly pressurized, the lower end portion of the operating shaft abuts the restricting portion.